In a fully switched network, hubs that would usually reside, for example, on an Ethernet network are replaced with one or more switches. These switches allow for a dedicated connection to, e.g., each workstation. A switch allows for many conversations to occur simultaneously. Before switches existed data could only be transmitted in one direction at a time, which was called half-duplex. However, by using a switch, a network is able to maintain a full -duplex Ethernet, wherein data can now be transmitted in both directions at the same time.
A function of a switch is to allow each workstation to communicate only with the switch instead of the workstations communicating with each other. With a fully switched network, data can be sent, for example, from workstation to switch and from switch to workstation simultaneously. Moreover, a switch is able to decongest network flow to the workstations so that the connections can transmit more effectively, for example, by receiving transmissions that were only specific to their network address. By using switches to transmit data in both directions simultaneously, network speed and capacity may be doubled when, for example, two workstations are trading information. That is, for example, if a network speed is 5 Mbit/s, then each workstation is able to simultaneously transfer data at 5 Mbit/s.
Fully switched networks employ, for example, twisted-pair or fiber-optic cabling, both of which use separate conductors for sending and receiving data. In this type of environment, Ethernet nodes can forego the collision detection process and transmit at will, since they are the only potential devices that can access the medium. As such, a fully switched network may be thought of as a collision-free environment.
Fibre Channel (FC) is a gigabit-speed network technology used for storage networking. There are three major FC topologies, describing how a number of ports are connected together. It should be understood that a port in FC terminology may be any entity that actively communicates over the network, and not necessarily a hardware port. This port may be implemented in a device such as, for example, a disk storage, a host bus adaptor (HBA) on a server, or a Fibre Channel switch.
A Point-to-Point (FC-P2P) is a first FC topology. With FC-P2P, two devices are connected back to back. This is the simplest FC topology, with limited connectivity. With a fiber channel switched fabric (FC-SW), all devices or loops of devices are connected to Fibre Channel switches, similar conceptually to modern Ethernet implementations. Advantages of FC-SW topology over FC-P2P or FCAL (described below) include: the switches manage the state of the fabric, providing optimized interconnections; multiple pairs of ports may communicate simultaneously; and/or failure of a port is isolated and should not affect operation of other ports.
With a fiber channel arbitrated loop (FCAL), all devices are in a loop or ring, similar to token ring networking. Adding or removing a device from the loop causes all activity on the loop to be interrupted. Moreover, the failure of one device causes a break in the ring. Fibre Channel hubs connect multiple devices together and may bypass failed ports. A loop may also be made by cabling each port to the next in a ring. As such, with FCAL topology, messages, for example, initiator-to-initiator messages, are transmitted over all the links that make up that loop. Additionally, for example, a fully switched network may be implemented with an FCAL to provide a switched FCAL network.
A field replaceable unit (FRU) may be, for example, a circuit board, part or assembly that can be quickly and easily removed from a personal computer or other piece of electronic equipment, and replaced by the user or a technician without having to send the entire product or system to a repair facility. That is, a system may include a number of FRUs, any one of which may need repair and/or replacement service throughout the use of the system. For example, an FRU, e.g., a network storage device component, may be in need for repair and/or replacement. A technician may, for example, arrive at a data center where the damaged network storage device component is located and swap out the damaged FRU for a replacement FRU, e.g., network storage device component.
After this service action that is intended to fix a problem with, for example, a back end switched storage network, a verification of the service action should be performed. For example, a verification should determine whether the replacement field replaceable unit (FRU) fixed the original problem. Additionally, the verification should determine whether the replacement FRU is a fully functional unit to use as a replacement.
However, verification may be difficult, particularly without risking customer I/O down an unverified path. That is, as explained above, with an FCAL topology, messages are transmitted over all the links that make up that loop. Thus, at present when a service action performed on a specific loop, this loop is placed into a logical “service mode”. In this mode the I/O is not routed down this path. This allows an engineer to remove or replace components in this loop without risking customer data. However, with this approach, utilization of the specific loop including, for example, all of the connected network storage devices, is interrupted while service and testing is performed.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.